New tech may let current graphics cards drive a $500 holographic display

Sound waves are key to making a cheap, color hologram.

Three-dimensional films and TVs may seem cutting-edge, but existing technologies all require optical tricks to create the illusion of depth (in some cases, very old tricks). The only truly 3D display technology we have, holography, has primarily been limited to displaying static images. That situation has slowly begun to change, but the existing technology is complicated and expensive, and it suffers from a slow refresh rate.

Now, some researchers have come up with a completely different method of creating the light pattern necessary to build a holographic image. The functional units in their device can be manufactured for pennies: the researchers suspect they could build a large holographic display for as little as $500, one that could potentially be driven by a commodity PC sporting a suite of high-end graphics cards.

The key to building a hologram is the ability of photons to interfere with each other, creating patterns where some regions have constructive interference and become bright, while others experience destructive interference and go dark. A carefully crafted diffractive can bend and redirect light so that this interference pattern recreates patterns of light that look as if they just reflected off the surface of a three-dimensional object. Most importantly, this 3D appearance is retained even as the viewer's perspective shifts around the surface.

We have very mature technology that allows us to create a static surface that consistently displays a single image. But to get that image to move or to replace it with a different image entirely involves wholesale modification to the hardware that is creating the diffraction pattern. Even assuming that you can calculate what the new configuration of the hardware must be (something that's not especially easy), you would then have to reconfigure the hardware and rescan light over it. The existing examples of hardware that can do this have some serious issues.

Most of them involve liquid crystal, micro-mechanical hardware that physically alters its configuration. The authors of the new paper provide a laundry list of this technology's limitations: "relatively low bandwidth, high cost, low diffraction angle, poor scalability, and the presence of quantization noise, unwanted diffractive orders, and zero-order light." (The latter factors create visual artifacts in the display image.)

The device the researchers have created instead involves an array of devices called anisotropic leaky-mode couplers. These devices act as waveguides for light while allowing the light travelling through them to be manipulated. When exposed to radio-frequency radiation, the hardware will form acoustic waves that alter the light travelling through them. This allows each coupler to rapidly alter the timing and direction of the light it emits in response to changes in the radio waves. By placing a number of them in close proximity, it's possible to get the light they emit to interfere (creating a hologram) and then change this hologram simply by altering the radio frequencies.

Other good features of the couplers are that they can be made to emit light with a single polarization, allowing a simple filter to cut out any imaging artifacts. And they can work with red, green, and blue light simultaneously, allowing a true-color hologram. This can also work with just about any light source.

You don't need many of these couplers to build a significant device; the authors estimate that about 500 of them would be all that you'd need to build a single horizontal line of a one-meter wide display. In the paper, they showed a device with 40 channels, and they're already testing one with 1,250 channels. The devices also easy and cheap to make. Their 40-channel hardware cost $50 to make at MIT's custom fabrication facility, but the author's estimate that an equivalent could be made at a commercial fabrication facility for somewhere in the area of $3.

As further progress has been made in getting graphics cards to generate holographic information and the radio frequency control signals are compatible with analog video displays, the authors think that a holographic display could probably be driven by a commodity PC with a bank of high-end graphics cards. The graphics cards would end up being the biggest expense in the hardware, so the actual array of couplers would only cost about $500 to make. Any reasonably bright color LED could provide the light source in this case. The end result would be a full-color hologram at standard video resolution with a refresh rate of about 30 fps.

I'm a little unclear as to what this article is referring to when they use the term hologram. Does this 'holographic display' refer to traditional holography, or are the authors describing some kind of Star Wars-style help-me-obi-wan-kenobi kind of deal?

Well, I was expecting the article to be about this kind of true 3D display, but then I remembered that "hologram" (and derivatives) as a technical term doesn't really mean the free-floating 3D models that the general public understands under the term "hologram." Then I was a bit disappointed.

"Help me, Obi-Wan Kenobi. You're my only hope."- All right, now what do I click? - Click "preferences."- Okay, I clicked preferences. - Now go to "default media browser".Okay, there's a little hourglass, and it's not letting me do anything.- It says "buffering." What is that? - Just give it a minute.All I'm trying to do is make an mpeg.All I'm trying to do is tell you to wait a minute.Okay, relax.Now click "import video file."All right.It's telling me I have to download RealPlayer 7.You know what? I'll just bring it to him myself.

"Help me, Obi-Wan Kenobi. You're my only hope."- All right, now what do I click? - Click "preferences."- Okay, I clicked preferences. - Now go to "default media browser".Okay, there's a little hourglass, and it's not letting me do anything.- It says "buffering." What is that? - Just give it a minute.All I'm trying to do is make an mpeg.All I'm trying to do is tell you to wait a minute.Okay, relax.Now click "import video file."All right.It's telling me I have to download RealPlayer 7.You know what? I'll just bring it to him myself.

"Any reasonably bright color LCD could provide the light source in this case"...?

An LCD is not really a light source, ... It incorporates a light source, the back light be it fluorescent or led, that shines thru the liquid crystal panel which acts as basically a changeable transparent slide. As my reading of your article suggests the image in this hologram comes from the interference of the combined anisotropic leaky-mode modulators and hence the lcd would be a pointless and inefficient source of Illumination.Or have I misread?

Well, I was expecting the article to be about this kind of true 3D display, but then I remembered that "hologram" (and derivatives) as a technical term doesn't really mean the free-floating 3D models that the general public understands under the term "hologram." Then I was a bit disappointed.

Still cool, though.

I think you are misunderstanding this. That is what they are talking about, it may have to come from the source up but given the light they choose to display with the color and spectrum behind it, they use to span the image, like when they had tupac on stage at that rap concert in hologram form, they could produce what you have shown on your link. This is true holographic tech they are talking about.

"Any reasonably bright color LCD could provide the light source in this case"...?

An LCD is not really a light source, ... It incorporates a light source, the back light be it fluorescent or led, that shines thru the liquid crystal panel which acts as basically a changeable transparent slide. As my reading of your article suggests the image in this hologram comes from the interference of the combined anisotropic leaky-mode modulators and hence the lcd would be a pointless and inefficient source of Illumination.Or have I misread?

If you were looking for a light source that could change between rgb rapidly lcd would still be a pretty poor choice from an efficiency perspective, your still filtering your original light source thru the whole screen when only using less than a third of it.Mirror chips redirecting three light source alla DLP, or even a rgb, or better yet a rgbcow, led array would seem much more logical.This is assuming the light source doesn't actually need a complete image per modulator which would be the only reason I can think of for using an LCD.

I'm pretty sure these are still driven by partial reflection to create the appearance of a hologram; the difference being that instead of a solid object being below the angled surface of glass (and the holographic image being above and beyond the glass), you have a set of lcd crystals below the glass, carefully controlled to produce interfering light patterns ehich reflect in a similar manner to that of a 3 dimensional object lying below.

In that sense...no, it's not an Obi-Wan Kanobi-style hologram, it's more the car-HUD/kid's toy style hologram. Still very neat though.

Well, I was expecting the article to be about this kind of true 3D display, but then I remembered that "hologram" (and derivatives) as a technical term doesn't really mean the free-floating 3D models that the general public understands under the term "hologram." Then I was a bit disappointed.

Still cool, though.

I think you are misunderstanding this. That is what they are talking about, it may have to come from the source up but given the light they choose to display with the color and spectrum behind it, they use to span the image, like when they had tupac on stage at that rap concert in hologram form, they could produce what you have shown on your link. This is true holographic tech they are talking about.

The Tupac rap concert "hologram" was nothing of the sort, assuming were both talking about the recent one with .. Snoop-dog I think? ... It was merely a cgi animation of Tupac projected on a scrim, basically a transparent screen normally a black fine bobbin netting or the like. Hardly an advance imaging technic as besides the cgi projected source similar things have been in theatre since the 18th century at least.

As best I can figure without reading TFA, this doesn't seem to be a real 3-dimensional object like that BTTF2 pic. I think what they mean when they say "a single horizontal line of a one-meter wide display" is 3D on a 2D screen like we already have, but without glasses.

Am I missing something? Where exactly do sound waves fit in to all this?

"the hardware will form acoustic waves that alter the light travelling through them. This allows each coupler to rapidly alter the timing and direction of the light it emits in response to changes in the radio waves."

Am I missing something? Where exactly do sound waves fit in to all this?

"the hardware will form acoustic waves that alter the light travelling through them. This allows each coupler to rapidly alter the timing and direction of the light it emits in response to changes in the radio waves."

I'm a little unclear as to what this article is referring to when they use the term hologram. Does this 'holographic display' refer to traditional holography, or are the authors describing some kind of Star Wars-style help-me-obi-wan-kenobi kind of deal?

A holograph is the 'negative' that is lighted to generate an image.A hologram is the image generated by a lighted holograph.

This system creates and lights virtual holographs in the same way that an LCD or LED monitor does "photographs".

This device is capable of generating real time animated holographic moving pictures. Whether they will be of the type generated by R2D2 delivering email or contained in a display box will depend on the exact form the hardware takes and what the limitations are on where the pixels are located relative to the signal source.

A similar effect is already available for audio. Multiple interfering inaudible signals interfere to produce audible sound at selected locations remote from the source. This generates actual 3D audio as opposed to the apparent 3D of stereophonic, quadrophonic, surround sound and similar systems.

PatentWhite paper from a company that has created acoustic interference 'speakers'(This is amazingly hard to search for. The search engines all insist I was trying to find acoustic weapons or advanced stereo effects)